The invention relates to a composite driving belt provided with a carrier and a plurality of transverse elements assembled slidably thereon.
Such Belt is generally known, e.g. described in U.S. Pat. Nos. 3,720,113 and 4,080,841. In the known belt, a carrier, alternatively denoted tensile element or tensile means, is composed as a package of a number of endless metal bands. The known belt may in particular be applied in a variable transmission, whereby the driving belt runs over pulleys, the substantial conical sheaves of which are adapted to be displaced axially relative to each other so that the running diameter of the driving belt over the pulley may vary. In turn, while the belt is in operation, the carrier or band package slides over a contact face, the so-called saddle part of the transverse elements. Also, the separate bands of the package slide relatively to each other during operation.
In practice the driving belt, in particular each of the bands, is under a very high tension, on the one hand to ensure a proper frictional contact between the pulleys and the transverse elements and on the other hand to properly conduct the transverse elements in the straight part of the driving belt, i.e. to prevent the belt, in particular the transverse elements in the straight trajectory part of the belt from splashing apart.
The efficiency of such Belt is rather high, but internal losses in the driving belt remain as result of frictional forces between the various parts, and as a result of such friction dissipated heat is to be removed. To meet these phenomena, the belt is in practice required to run in an oiled environment.
One manner of addressing these practical problems is addressed by European patent application 0014014, which shows a manner of draining oil to the locations where sliding contact may take place and where heat is to be removed. The main important contact areas dissipating heat are between pulley and transverse element, between saddle and tensile element and between the bands of the tensile element. According to the teaching of this publication, one flat side of each band should be profiled, such that when incorporated in a belt, this side abuts a band side without such profiling. In this manner an important oil drain is achieved by the profiling towards both sliding contacts in which a band is involved, viz. Mutually between the bands, and between the inner band of a carrier and the saddle of transverse elements. The document thereby teaches that an improved mutual friction between the mutual bands disposed around each other leads to an efficiency increase.
From commercialised belts it is found that such profiling is applied on the inner side of such constituent metal rings of a band. This practice is also suggested by the figure of said EP publication and is confirmed by the recent patent publication EP-A-0909907.
A draw back of the known belts is that when the belt is operated in rotation transfer modes outside medium, i.e. outside ratio 1, the efficiency decreases, in particular when the belt is operated close to so called low (LOW) or over drive (OD) mode. It is an object of the current invention to address this phenomenon, i.e. to improve the efficiency in these areas in a safe and reliable manner, i.e. without endangering the proper oiling of the various sliding contacts related to the functioning of the known belt.
According to the invention this may in particular be reached by a construction in accordance with the below features. A construction having the feature of the invention surprisingly directs away from above said common practice of contacting, realises an improved overall efficiency through a decreased amount of friction in the above said ranges, already by the mere omission of the oiling profile. Moreover, the measure according to the invention enhances the belt""s lifetime by virtue of the effect that the decreased amount friction also occurs in the much-used parts of a transmissions range of ratios. Thus according to an insight partly underlying the invention, a distinction should be made between the shape of contact faces required in a bandxe2x80x94band contact and in a band-element contact. The radial inward directed carrier surface is relatively very smooth, at least diminished by a half compared to the roughness from known belts, while a predetermined profiling is omitted from this surface, i.e. no separate aimed treatment of the profiling can be recognised in the surface.